Answer: a
Explanation: The carbon cycle naturally has 2 parts, the terrestrial (movement of carbon through terrestrial ecosystems) and the aquatic (which is related to carbon movements through marine ecosystems).

Answer: c
Explanation: The different forms of precipitation are rain (water drops with diameter at least 0.5mm), snow (ice crystals/flakes with an average density of 0.1g/cm3), drizzle (water drops less than 0.5mm), glaze (rain touches ground at 0oC), sleet (frozen raindrops) and hail (pellets or lumps of ice of >8mm size).

Answer: c
Explanation: A nutrient cycle occurs within ecosystems and it is the movement of organic and inorganic matter between different members of the ecosystem. This is regulated by the food chains that use these for production and release them into atmosphere on decomposition.

6. Living organisms can use Nitrogen (N2) as it occurs in the atmosphere.
a) True
b) FalseView Answer

Answer: b
Explanation: The living organisms cannot use N2 to synthesise organic compounds. N2 is converted to NH3 by nitrogen fixing bacteria and then to nitrate by nitrifying bacteria which can then be used by organisms.

Answer: a
Explanation: Nitrogen rich fertilizers are often overused. As a result, nitrogen gets into the soil, favouring growth of weeds. It is also washed into waterways, where again it causes growth of aquatic weeds.

8. Which of the following cycle does not have a gaseous state?
a) Oxygen
b) Nitrogen
c) Carbon
d) PhosphorousView Answer

Answer: d
Explanation: Phosphorous is present as inorganic phosphate PO43-. It is released from rocks and sediments. It is absorbed by plants and is incorporated into the nucleic acids.

9. In water cycle, the process can be explained in equation form as
Evaporation + __________ = Precipitation
a) Infiltration
b) Ground water
c) Transpiration
d) Run-offView Answer

Answer: d
Explanation: Water cycle has three components – evaporation, run-off and precipitation. Transpiration is included in evaporation. Run-off is that part of water which is not evaporated.

Answer: c
Explanation: Denitrification refers to the process of reduction of nitrates back to nitrogen gas. Pseudomonas bacteria makes this happen. It uses nitrates in soil to carry out respiration and consequently, produce nitrogen gas.

14. How many reservoirs are there in the oxygen cycle?
a) 3
b) 2
c) 5
d) 4View Answer

Answer: a
Explanation: The three main reservoirs are atmosphere (air), biosphere (the global sum of all ecosystems) and Earth’s crust.